U.S. Pat. No. 3,991,800 discloses the concept of slitting the bark on a log in a helical pattern and than peeling off the bark in a continuous operation. This technique is particularly effective for removing bark having relatively long stringy fibers such as present on cedar and eucalyptus trees. The bark slitting is disclosed as being performed by a ring-type debarker having modified tools on its swing arms. The slitting operation cuts through the stringy fibers at regular intervals so that the bark can then be peeled cleanly from the log in a helical strip. The modified debarker is positioned in advance of a standard ring-type debarker so that the logs pass axially through both machines.
It is preferred to have the slit through the bark made during the bark slitting operation be performed such that the bark adjoining the slit is not scuffed and partially peeled. Otherwise, the stringy bark tends to bunch and foul the bark slitting ring.
Bark thickness and resistance to cutting also varies. Hence, it is preferred to be able to control the cutting pressure so as to cleanly cut through the bark, and yet not unduly score the underlying wood. A further need is ease of removing the slitting tools for sharpening or replacement.